Radiation exposure as a consequence of diagnostic and therapeutic radiological procedures to the child involves a significant proportion of the pediatric population. The potential risk associated with radiation exposure is significantly greater in children than adults (i.e., leukemogenesis and carcinogenesis of the breast). Accurate knowledge of the absorbed dose in an organ sensitive to radiation damage is critical in the evaluation of the risk-benefit ratio. Oak Ridge National Laboratory has pioneered efforts to quantitate organ-absorbed dose based on calculational models that use Monte Carlo radiation transport codes and mathematical models of the human body. While computational and experimental methodologies have been developed and performed in order to estimate organ dose in adults, relatively little effort has been devoted to similar estimates for children based upon actual physical measurements. Pediatric organ doses have been estimated using transformed adult phantoms. These phantoms suffer from geometrical limitations in their portrayal of the human child. These limitations are critical in the estimation of active bone marrow dose. This proposal is a collaborative effort between Children's Hospital National Medical Center and Oak Ridge National Laboratory. The objective is the development of anatomical child phantoms from computerized axial tomography scans of pediatric patients and cadavers for the following classes of patients: newborn, 1 year, 5 year, 10 year and 15 year. These digital phantoms will be input to detailed Monte Carlo radiation transport calculations resulting in calculated organ-absorbed doses for common pediatric diagnostic examinations. Additionally, normalized organ-absorbed doses for pediatric sized patients for common diagnostic x-ray projections will be measured in anthropomorphic phantoms. These measurements will be used to verify the accuracy of the calculational model.